Aeronautical propeller



Sept. 11, 1962 P. F. FERREIRA 3,053,325

AERONAUTICAL PROPELLER Filed Oct. 25, 1961 2 Sheets-Sheet 1 Paul F Ferreira l N VEN TOR.

Wynn; H

Attorney:

Sept. 11, 1962 P. F. FERREIRA 3,053,325

AERONAUTICAL .PROPELLER Filed Oct. 25, 1961 2 Sheets-Sheet 2 Paul FFerreira INVENTOR.

BY 2mm 3,053,325 Patented Sept. 11, 1962 3,653,325 AERONAUTICALPROPELLER Paul F. Ferreira, Box 111, Honolulu, Hawaii Filed Oct. 25,1961, Ser. No. 147,529 6 Claims. (Cl. 170159) This invention relates topropellers and particularly to propellers for aircraft.

Briefly, the invention comprises a propeller having an enlarged arrowhead shaped tip portion which has a concave forward face thatsubstantially improves the efficiency of the propeller.

Accordingly, it is a primary object of the invention to provide apropeller having extremely high efiiciency for its diameter and pitch.

It is still another object o fthe invention to provide a propeller whichis so designed that it will efficiently absorb a large amount of powerparticularly since its tip speed is reduced.

It is still another object of the invention to provide a propeller whichwill operate more efficiently at extremely high tip speeds.

It is still another object of the invention to provide an improvedpropeller which is suitable for use on aircraft, helicopters, and marinecraft.

It is still another object of the invention to incorporate theadvantages and efficiencies of the principles of a delta wing for use inpropellers for improving the efiiciency thereof, particularly at the tipportions which are normally operated in the vicinity of sonic speeds.

These together with other objects and advantages which will becomesubsequently apparent reside in the details of construction andoperation as more fully hereinafter described and claimed, referencebeing had to the accompanying drawings forming a part hereof, whereinlike numerals refer to like parts throughout, and in which:

FIGURE 1 is a front elevational view of a preferred form of myinvention;

FIGURE 2 is an enlarged end or plan view of the propeller shown inFIGURE 1;

FIGURES 3, 4, 5, 6, 7, 8, 9 and 10 are enlarged crosssectional viewstaken on lines 33, 44, 5-5, 6*6, 77, 8-8, 9-9 and 1010, respectively onFIG- URE 1.

FIGURE 11 is a front elevational view of a modified form of myinvention;

FIGURE 12 is a horizontal cross-sectional view taken substantially onthe plane of line 12-12 of FIGURE 11;

FIGURE 13 is a vertical cross-sectional view taken substantially on theplane of line 1313 in FIGURE ll;

FIGURE 14 is a cross-sectional view taken substantially on the plane ofline 1414 in FIGURE 11;

FIGURE 15 is an elevational View of a portion of a third form of myinvention;

FIGURE 16 is a cross-sectional view taken substantially on the plane ofline 16-16 of FIGURE 15; and

FIGURE 17 is a rear elevational View of a fourth form of my invention.

Referring to the drawings, and particularly FIGURES 1 through 10, it canbe seen that my propeller it includes a flat circular central hub 12 andconventional propeller blades 14 and 16 projecting radially fromopposite sides of the hub 12 and formed integrally therewith. The blades14 and 16 are of conventional air-foil crosssectional shape and thetrailing edge and leading edge of each blade diverge from one another ina radially outward direction. As can be seen in FIGURES 8, 9 and 10, theblades are twisted so that the radially inner portions of the bladeshave a greater angle of attack or pitch than the radially inner portionthereof because of the greater linear velocity of the radial outerportions. It is also to be noted that the back sides of the blades areflat as shown at 18 and the forward surface of the blades are convex asshown at 29.

The ends of the blades 14 and '16 are secured to delta orarrowhead-shaped tiups 22 and 24, respectively. Since the tips 22 and 24are identical to one another, only the tip 22 will be described indetail.

The delta-shaped tip 22 is defined by a slightly convex outer leadingedge 26, a slightly convex inner leading edge 28 and a substantiallyradially extending trailing edge 36 The back side of the tip 22 issubstantially flat as shown at 3-2 and is coplanar with the back surfaceof the outer end portion of blade 14 as shown in FIGURE 7. Two convexridges 34 and 36 are formed on each side of the forward face of the tip22, and these ridges extend in slightly curved paths which are parallelto the leading edges 26 and 28. The forward face of the tip 22 ishollowed out between the ridges 34 and 36 so as to form a concaveportion 38. As shown more clearly in FIGURES 3, 4 and 5 the concaveportion 38 and the ridges 34 and 36 gradually decrease in thickness asthey approach the trailing edge 30 so as to provide a relatively sharptrailing edge. It is also to be noted that any cross-section such as3-3, 44 and 5-5 taken through the tip 22 by a plane perpendicular to thelongitudinal axis of the propeller is of streamlined airfoil shapesimilar to the cross-sectional shape of the blades 14 and 16. Therefore,it is apparent that when the propeller rotates in a counterclockwisedirection as viewed in FIG- URE 1 and indicated by the arrows R that thedirection of airflow over the tip 22 is substantially parallel to thesection lines 33, 44 and 5-5, and also the direction of flow of this airis also generally perpendicular to the longitudinal axis 40 of thepropeller. Therefore, since the air flowing over the tip portion 22 isin effect flowing over a streamlined airfoil of the shape shown inFIGURES 3, 4 and 5 the relative movement between the air flowing overthe tip 22 and the surfaces of the tip 22 create a great amount ofthrust in the direction of the arrows T shown in FIGURES 2. A port-ionof this thrust is created by the positive angle of attack of the fiatsurfaces 32 of the tip. However, most of the thrust is created by theair flowing over the convex ridges 34 and 36 into the concave portion28. The is because in flowing over the ridges the velocity of the air isincreased thereby creating a reduced pressure on the back sides of theridges and in the depression or convex portion 36.

Due to the relatively large area of the tip portions 22 and 24, theyobviously absorb a great deal of power in relation to the blades 14 and16 "because they are rotating or traveling at a greater linear speed.

The tips 22 and 24 are in effect miniature delta wings. Therefore, theyhave all the advantages and characteristics of delta wings which areknown to have improved aerodynamic characteristics at extremely highspeeds, particularly speeds in the vicinity of sound and above.

It is to be noted that the forward surface of the outer end of eachblade 14 and 16 merges smoothly into the ridges 36 as shown at 42.

FIGURES 11 through 14 illustrate a modified form 44 of my propeller. Thepropeller 44 comprises a circular hub 46 integrally formed with S-shapedblades 14 and 16 of circular cross-section. These blades terminate inand merge with delta-shaped tips 22 and 24' of identical configurationand size. The tips 22 and 24 except their leading edges 26 and 28 arestraight. Also, it is to be noted that the blades 14' and 16' areconnected with the trailing edges 30 of the tips and merge and blendinto the rear end of the edges 36'.

While the blades 14' and 16' are shown as being circular incross-section it is apparent that they could be of streamline orteardrop cross-sectional shape.

In the third form of my invention illustrated in FIG- URES and 16, thetips are substantially of the same design and configuration as shown inFIGURES 1 and 11. One of the tips is shown at 22 and differs from theother forms primarily in that a reinforcing rib 48 extendslongitudinally down the center of the tip and projects from the forwardface thereof. The rib 48 is substantially triangular in cross-sectionand has a pointed leading edge a shown at 50. The primary purpose of therib 48 is to reinforce and strengthen the relatively thin centralportion of the tip, particularly where it is recessed as shown at 38".The tips are mounted on the ends of blades 14" which are as illustratedin FIGURE 15 circular in cross-section. The blades on which the tips aremounted are substantially the same shape and design as illustrated at 14and 16' in FIGURE 11.

FIGURE 11 illustrates a fourth form of my invention which differsprimarily over the previous forms in that the blades 14" and 16" aresubstantially straight in a radial direction rather than being F-shapedas illustrated in FIGURES 11 and 15. However, these blades are eithercircular or teardrop-shaped in cross-section. While the blades are shownsupporting tips 22 and 24" of the same design illustrated in FIGURE 15,these tips may be of the designs illustrated in FIGURES 1 and 11 ifdesired.

The hubs of all the propellers illustrated are preferably provided witha central bore 13 for receiving a conventional drive shaft. The hubs mayalso be provided with conventional bores 15 (see FIGURE 1) arranged in acircular pattern around the central bore 13 for receiving bolts whichextend through a radial flange on a drive shaft.

If desired, the blades such as 14 and 15 in FIGURE 1 of the propellersmay be provided with dihedral, particularly if they are to be used inhelicopters. By dihedral, it is meant that the outer ends of thepropeller blades are tilted forwardly or backwardly in relation to thehub 12.

By providing the propeller blades with the tips 22 and 24, it ispossible to make a propeller of much smaller overall diameter which willabsorb as much power as a conventional propeller of considerably largerdiameter. The advantages of this are readily apparent. For example, itpermits the landing gear of the aircraft on which the propellers areused to be made much shorter thereby saving weight and materials, and itreduces the tip speed of the propellers thereby permitting them tooperate more efficiently.

The foregoing is considered as illustrative only of the principles ofthe invention. Further, since numerous modifications and changes willreadily occur to those skilled in the art, it is not desired to limitthe invention to the exact construction and operation shown anddescribed, and accordingly all suitable modifications and equivalentsmay be resorted to, falling within the scope of the invention asclaimed.

What is claimed as new is as follows:

1. A propeller comprising a blade, means for securing one end of theblade to a power source, the other end of said blade secured to anenlarged tip of deltoid shape, said tip having leading edges projectingforwardly of the leading edge of said blade and converging to a point,convex ridges formed on the forward surface of the tip parallel to andadjacent to said leading edges of said tip.

2. A propeller as defined in claim 1 wherein said tip is provided with aconcave area between said ridges.

3. A device as defined in claim 1 wherein said ridges and the thicknessof said tip at said concave area gradually decrease in thickness in adirection toward the trailing edge of the tip.

4. A device as defined in claim 3 wherein said blade is circular incross-section.

5. A device as defined in claim 4 wherein said blade extends in anarcuate path between said securing means and tip.

6. A device as defined in claim 3 wherein a reinforcing rib is formed onthe forward surface of said tip and extends along the median linethereof.

References Cited in the file of this patent UNITED STATES PATENTS1,427,307 MaKenney Aug. 29, 1922 2,422,388 Billings June 17, 19472,511,502 Gluhareff June 13, 1950

